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CVE-2026-8981 - Before 4 Plugin

CVE-2026-8981

The Custom Block Builder WordPress plugin before 4.3.0 does not consistently check the unfiltered_html capability across all paths that write to its block template code fields, allowing administrators on multisite installations (or single-site installs with DISALLOW_UNFILTERED_HTML defined) to inject arbitrary JavaScript that executes for any visitor of pages embedding the affected block.

CVE-2026-8981

LOW CVSS 3.5 Published 2026-06-09 Updated 2026-06-09
AI Risk Low (30/100) Active Exploit: No strong signal Published Exploit: No public exploit references Priority: P5 Monitor
Severity Band LOW
CVSS Vector CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:U/C:L/I:L/A:N
Affected Components 2
Reference Links 1
AI Risk Engine Low (30/100)
Exploitability Low
Active Exploitation No strong signal
Published Exploit Status No public exploit references

Threat Timeline

  1. 2026-06-09 CVE published and first recorded in the threat feed.
  2. 2026-06-09 Record updated with latest vulnerability metadata.
  3. 2026-06-09 AI technical context refreshed for mitigation and impact guidance.
  4. Now Monitoring for follow-up changes, linked references, and new related CVEs.

AI Context

Machine-generated threat intelligence

AI Updated 4 hours ago

AI enriched 4 hours ago (2026-06-09 21:25 UTC)

Technical Summary

The Custom Block Builder WordPress plugin before 4.3.0 does not consistently check the unfiltered_html capability across all paths that write to its block template code fields, allowing administrators on multisite installations (or single-site installs with DISALLOW_UNFILTERED_HTML defined) to inject arbitrary JavaScript that executes for any visitor of pages embedding the affected block.

Potential Impact

Severity is LOW (CVSS 3.5). Depending on deployment context, affected components may be exposed to unauthorized actions or data integrity risk.

Exploitability Assessment

Exploitability is assessed as Low based on severity and technical exposure profile.

Primary risk drivers: severity and technical exposure profile

Mitigation Recommendations

Validate affected product versions, prioritize patching, and monitor references for vendor remediation guidance. If immediate patching is not possible, apply compensating controls and limit exposure of vulnerable surfaces.

Detection & Monitoring

Track authentication anomalies, unexpected file writes, and suspicious plugin API activity around affected components.

Business Impact Lens

AI risk score 30/100 (Low, Low) with priority P5 Monitor. Prioritize remediation where affected components process customer data, admin sessions, or Internet-exposed workflows.

Affected Products

Before 4 PLUGIN · before-4 Affected: < 4.3.0 Fixed in: 4.3.0
Custom Block Builder PLUGIN · custom-block-builder Affected: < 4.3.0 Fixed in: 4.3.0
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